Cartridge locator

ABSTRACT

A precision cartridge stock locator for use in stamping dies and the like includes a bushing, a headed pilot pin slidable within a bearing in the bushing, a polyurethane spring acting on the head of the pin, and a retainer for the spring.

te States Rupert Sept. 11, 1973 CARTRIDGE LOCATOR [76] Inventor: Ronald E. Rupert, 231 N. College St., Palmyra, Pa. 17078 [22] Filed: June 8, 1971 211 Appl. No.: 150,998

[52] US. Cl 72/461, 83/228, 267/153 [51] Int. Cl B2111 11/22 [58] Field of Search 72/461; 83/228, 467,

[56] References Cited UNITED STATES PATENTS 4/1963 Levine 83/637 11/1927 Furber 1/1941 Cunningham 83/467 2,827,120 3/1958 Davidson 83/228 3,434,708 3/1969 Hawk 267/153 FOREIGN PATENTS OR APPLICATIONS 1,063,754 3/1967 Great Britain 267/153 1,066,745 4/1967 Great Britain 267/153 Primary Examiner-Charles W. Lanham Assistant Examiner-Gene P. Crosby Att0mey-Schellin & Hoffman [57] ABSTRACT A precision cartridge stock locator for use in stamping dies and the like includes a bushing, a headed pilot pin slidable within a bearing in the bushing, a polyurethane spring acting on the head of the pin, and a retainer for the spring.

2 Claims, 4 Drawing Figures Patented Sept. 11,1973

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\7 i l5 g INVENTOR RONALD E. RUPERT BY/JM W ATTORNEYS CARTRIDGE LOCA'IOR BACKGROUND OF THE INVENTION In progressive die work and in other mechanical operations, it is necessary to position the stock accurately at each station before work is done on it. This may be accomplished by piercing a hole in the stock and providing each station with a pilot pin which just fits into the hole. If the stock has been advanced to the correct position, the pilot pin will enter the hole and the desired work can be carried out. If the stock is closed to the desired position on partly entering the hole the pilot pin should be able to pull the stock into the correct position. However, if the stock is so far off position that this is not possible, there should be no damage to the apparatus, the pilot pin, or the stock.

The prior art locators suffer from various disadvantages. They are bulky and require considerable space, they usually have but limited pressure potential, and they contain several parts, which make servicing difficult.

It is therefore an object of the present invention to provide a cartridge stock locator which may be incorporated within a single plate of the die. It is a further object of the invention to provide such a device with a spring loaded pilot pin which will enter the locating hole if the stock is properly advanced, will pull the stock into position if the pin partly enters the locating hole of slightly off position stock, or will retract completely within the cartridge without causing damage if the pin does not contact the locating hole.

BRIEF SUMMARY OF THE INVENTION The present invention provides a cartridge stock cator with a spring loaded pilot pin. The cartridge structure makes it possible to incorporate the device within a single plate of die. The spring loading assures that no damage will result to the apparatus, the pin, or the stock if the pin meets resistance and cannot pull the stock into position.

The cartridge comprises a bushing with an upper bore to receive the spring and the head of the pilot pin, and a smaller diameter lower bore to provide a bearing surface within which the pilot pin slides with a slip fit. The lower end of the pin is pointed so that it can at least partly enter the locating hole of slightly off position stock. The spring, held in position by a retainer secured to the upper end of the bushing, has sufi'icient power to hold the pilot pin in the advanced position so that it can pull the stock into position, if necessary; yet, if the pin meets resistance, the spring will collapse to permit the pin to retract into the bearing without causing any damage. A small hole in the retainer prevents air locks which might result from the slip fit of the pin.

The overall dimensions of the cartridge are not especially critical. They may be selected to permit use of the retainer in existing equipment or, if holes to receive the device must be provided, the cartridge will be kept as small as efficient operation will permit.

DETAILED DESCRIPTION OF THE INVENTION Further details of the cartridge stock locator are illustrated in the embodiment shown in the drawing in which:

FIG. I is a side view of the cartridge locator with the lower end of the pilot pin in the locating hole of the stock;

FIG. 2 is a sectional view along line 22 of FIG. 1;

FIG. 3 is a similar sectional view but with the spring collapsed and the pilot pin retracted within the bearing because the stock is off postion;

FIG. 4 is a sectional view along line 3-3 of FIG. 3.

The precision cartridge stock locator shown in the drawings and indicated by 10 includes bushing 11, provided with upper bore 12 and lower bore 13 of smaller diameter to provide a bearing surface for the pin. Pilot pin 14 consists of a cylindrical portion 15 which slides within the bearing surface with a slip fit, head 16, and pointed lead end 17. The lead end may be parabolic in shape, conical, ballshaped, or a combination of these. It is merely necessary that the lead end be able to enter the locating hole of slightly off position stock. The length of the bearing surface in the lower bore should be approximately 1% to 2% times, preferably approximately two times, the diameter of the pilot pin.

Spring 18, consisting of a polyurethane elastomer in the form of a tube, is disposed above head 16 of the pilot pin. The spring should be capable of causing the pilot pin to extend fully, yet it should collapse to one quarter of its length with no more than a percent increase in the pressure against the pilot pin. The spring shown in the drawing has serrations on the outside of the tube. However, the serrations may be on the inside of the tube, they may be on both the inside and the out side, or the tube may have no serrations. The tube may consist of a pile of washers. Polyurethane having a durometer hardness of approximately 80 on the Shore A scale to approximately 70 on the Shore D scale provides a satisfactory locator spring. Mechanical springs may be used in some cases in place of the polyurethane spring, although these exert only a fraction of the force exerted by a polyurethane spring.

Retainer 19 is positioned at the top of the bushing to hold spring 18 in place. Relief opening 20 in the retainer prevents air locks which might otherwise result from the slip fit of the pilot pin against the bearing surface. The retainer may be held in position in the bushing of preening, riveting, welding, etc.

The overall length ofthe collapsed cartridge (i.e., with the pilot pin completely retracted within the bushing) should be approximately three to approximately six times the diameter of the pilot pin. The outside diameter of the cartridge is not critical. This dimension may be selected to make it possible to use the device in existing equipment, or it may be selected simply to provide a compact but efficient device. If desired, the bushing may have one or more heads or collars. The bushing may be threaded or it may be press fitted in the die.

A cartridge stock locator, assembled as described, is positioned within an existing locator pinhole in the die, or in a hole made for that purpose. Obviously, there will be a stock locator for each station of the apparatus. A locating hole 21 is pierced in stock 22, and the stock is caused to advance in the apparatus in the usual manner. If the stock is correctly positioned at a station, the pilot pin will enter the locating hole and the desired operation can be performed. If the stock is slightly off position, the lead end of the pilot pin will enter the locating hole and will then pull the stock into the correct position. If the stock is so far off position that this is impossible, the resistance offered by the stock will cause the spring to collapse so that the pilot pin will retract lead end, a bearing surface for said pilot pin within said bushing, a spring acting against the head of said pilot pin, and a retainer holding said pin within said bushing, said spring is a tube of polyurethane having a durometer hardness of from about 80 on the Shore A scale to about on the Shore D scale.

2. A cartridge stock locator as defined in claim 1 wherein said tubular polyurethane spring has serrations on at least one side of said tube.

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1. A cartridge stock locator comprising a bushing, a headed pilot pin slidable within and completely retractable within said bushing, said pilot pin having a pointed lead end, a bearing surface for said pilot pin within said bushing, a spring acting against the head of said pilot pin, and a retainer holding said pin within said bushing, said spring is a tube of polyurethane having a durometer hardness of from about 80 on the Shore A scale to about 70 on the Shore D scale.
 2. A cartridge stock locator as defined in claim 1 wherein said tubular polyurethane spring has serrations on at least one side of said tube. 